1. Field of the Invention
This invention relates to clutch type systems and in particular to a torque responsive actuation devices that include roller bearings arranged to travel along helix tracks to open and closing opposing pulley halves for a belt driven power train as is commonly used for snowmobiles, and the like.
2. Prior Art
The present invention is in a torque responsive actuation device that incorporated bearings arranged travel along helix tracks, functioning as a clutch for a belt driven power train. The invention improves upon prior systems by providing for radiusing either the bearing or track whereon it travels, the bearing to travel along a center line of the helix track, with bearing travel to spread apart pulley halves wherearound a continuous drive belt is positioned. The pulley opening is matched by closure of a drive clutch. So arranged, based upon engine speed, the one clutch will open its pulley, thereby reducing the radius of pulley that the belt travels around, as the other clutch closes its pulley, thereby increasing the pulley radius. The belt is tightly maintained within the pulleys with changes in applied torque producing changes in the radiuses of the respective clutch pulleys.
Examples of earlier devices for varying pulley diameter responsive to torque are shown in U.S. Patents to: Steurer, U.S. Pat. No. 3,722,308; Togami, et al. No. 4,173,155; Huff, U.S. Pat. No. 4,378,221; Marier, U.S. Pat. No. 4,585,429; and Smith, et al, U.S. Pat. No. 5,403,240. The desirability of decreasing friction and diminishing binding between bearings and the helix tracks whereon they travel was recently recognized in a patent application of the present inventor, entitled “Torque Responsive Actuation Device for a Belt Drive System” U.S. patent application Ser. No. 08/323,611, filed Oct. 17, 1994, now U.S. Pat. No. 5,516,333 that the present invention improves upon.
In applicant's earlier patent application, only the helix cam tracks that individual roller bearing travel along were shown radiused, each presenting a convex surface therealong. These curved surfaces provide for centering the roller of each roller bearing as it rolls therealong, providing for a very smooth clutch upshift and backshift relative movement with less component wear than earlier clutch arrangements experience. The present invention further recognizes that any torque sensing type of clutch arrangement that utilizes a bearing a cam can include a radiusing of either of the opposing bearing or helix surfaces to obtain the benefits as set out in the above cited U.S. Patent Application.